Adenosine 3',5'-monophosphate dependent protein kinase of uterus in euthyroid and hypothyroid rats

Nature of cyclic AMP-dependent protein kinases from the uterus of euthyroid and hypothyroid estrus rats was investigated. There was no significant difference between euthyroid and hypothyroid rats in the protein content and the total activity of cyclic AMP-dependent and independent protein kinases of the soluble fractions of uterus tissues. However it was clearly demonstrated that the type I isozyme remarkably decreased in hypothyroid rats in comparison with that of euthyroid rats. The ratio of type I to type II was 1.26 in euthyroid rats and 0.41 in hypothyroid rats. The kinetic properties of the type I and the type II isozymes from both groups of rats showed similar patterns in NaF, Mg2+, cyclic AMP, histone and ATP. It was not observed that the apparent Km values of both the isozymes for histone and ATP were significantly different between euthyroid and hypothyroid rats. Data obtained from these experiments suggested that the thyroid hormone affected the metabolic processes of the uterus through alteration of the isozyme distribution of cyclic AMP-dependent protein kinase.